The interior spaces of structures exposed to extreme heat are typically cooled by active refrigeration and evaporative cooling systems. Unfortunately, such systems demand a substantial amount of electric or other type of external power which generates large operating costs in addition to the initial cost of the system. Refrigeration systems use almost as much electrical energy to power fans and pumps, and require constant replenishment of their water supply.
The cost of active cooling systems is not always prohibitive in structures designed for human habitation or use, such as homes, office buildings, factories and the like. However, cooling systems are often desirable in other types of structures where the installation and operating costs of active cooling systems cannot be justified, such as relatively small or remote structures designed to house livestock or electrical or fiber-optic equipment. It is often not feasible to bring electricity to a remote structure or to provide for the generation of electricity on-site, or to provide an alternative source of power. As a result, active cooling systems often cannot be used in situations in which some form of temperature control is highly desirable.
In an attempt to solve the above problems, passive cooling systems have been developed to provide cooling by passively radiating heat to the night sky. One such system is disclosed in commonly assigned U.S. Pat. No. 5,070,933 to Baer, the complete disclosure of which is incorporated herein by reference. In this cooling system, a plurality of plastic containers filled with water and insulation are mounted to the roof of the structure. The insulation contains vertical passages so that the water may flow between the upper and lower walls of the container. During the evening, relatively cold water, chilled by the night atmosphere, flows downwardly through the vertical passages in the insulation towards the lower wall of the container and cools the interior of the structure by heat transfer. During the day, the insulation and water minimize the penetration of heat from the outside.
One problem with existing passive cooling systems such as the above referenced patent is that the plastic containers filled with water and insulation are heavy. Therefore, these systems typically include a large and relatively expensive support system to hold the plastic containers against the roof of the structure. In addition, gravity and thermal stresses eventually cause the heavy plastic containers to sag away from the roof Of the structure. This decreases the heat transfer from the water to the cool night air because the plastic containers are no longer in intimate contact with the roof.
Another problem with existing passive cooling systems is that the plastic containers will deform with severe changes in temperature. Since thermal deformation tends to have a permanent effect on plastic (plastic, unlike metals, does not have a "memory" for its original shape), the plastic containers will not completely return to their original shape after these severe temperature changes. This permanent deformation of the containers can have a detrimental effect on the heat transfer characteristics of the temperature regulating system.